Resilient seals of basic C-shaped cross-section are known and used in numerous applications. However, there can be some drawbacks to the basic C-shaped type of seal. For example, in certain circumstances where it is desired to obtain virtual hermetic sealing, in which leakage rates are lower than 1E-9 mb-l/s, a basic C-shaped seal may have limitations on re-use or repositioning due to low springback, and may lack the ability to achieve the desired combination of acceptable springback and high sealing force. The importance of springback and the maintenance of sealing force are significant in such environments as elevated temperature sealing of relatively flexible pressure containment structures, because, for example, at operating pressures and temperatures, a joint sealed by a resilient seal will usually experience a widening of the distance between its sealing faces.
Various solutions have been developed to achieve high springback and sealing force. For example, a basic C-shaped cross-section seal may be reinforced by a secondary element, such as, for example, a C-shaped seal having a helically-wound, toroidal "garter" spring nested inside the C-shaped cross-section of the seal as disclosed in U.S. Pat. No. 5,022,663. Another disclosure for achieving high springback and sealing force employs the use of multiple-ply C-shaped cross-section seals as disclosed in U.S. Pat. No. 4,218,067. Yet another disclosure for achieving high springback and reduced sealing force is disclosed U.S. patent application Ser. No. 09/228,292, filed Jan. 11, 1999, entitled Resilient Sealing Ring, in the names of Horace P. Halling and Paul L. Porter.
Also, some types of seals, including some discussed above having reinforcement features, suffer from the disadvantage that they manifest a tendency to retain the fluids they are sealing. For example, they tend to retain viscous fluids and plating solutions. An example of fluid retention occurs when the fluid under high pressure enters the channel formed by the concave central area of the C-shape and penetrates between the coils of a garter spring. When the pressure is reduced, some fluid remains within the close-coiled spring inside the channel inside the C-shape even after the fluid chamber being sealed has otherwise been evacuated or emptied. For example, entrapment of fluids in the channel inside the reinforced C-shape may occur during plating operations at the time of seal manufacture or during operation of the seal. The fluids may become entrapped in the reentrant channel inside the reinforced C-shape due to capillary attraction or due to the viscosity of the fluid. Accordingly, these seals require effective masking if fluid retention is to be avoided.